Chiari Malformation Type 2

Excerpt

At the end of the nineteenth century, the pathologists Julius Arnold (1835-1915) and Hans Chiari (1851-1916) described a complex clinical and pathological condition involving deformity of the cerebellum and brainstem in children. Chiari malformations are now defined as a spectrum of hindbrain abnormalities involving the cerebellum, brainstem, skull base, and cervical cord. According to the type of herniation of the brain tissue displaced in the spinal canal and the characteristics of the anomalies of the brain or spine development, 4 types of Chiari malformations have been classified. Together with basilar invaginations, Chiari malformations represent the most common craniocervical junction malformations seen in adults.

Chiari malformation type 2 or Chiari 2 malformation, commonly referred to as Arnold-Chiari malformation, is usually associated with spina bifida and is characterized by caudal displacement of the cerebellar vermis, brainstem, and fourth ventricle. Despite its name, rather than a continuation of a spectrum with Chiari 2 malformation representing a severe version of Chiari 1 malformation, these malformations represent distinct disease processes with overlapping radiographic findings. (see Image. Chiari Malformation Types 1 and 2). Chiari 2 malformation can be associated with numerous additional findings, most commonly hydrocephalus and syringomyelia. Clinically, Chiari 1 malformation can be an asymptomatic hindbrain hernia, while Chiari types 2, 3, and 4 are congenital and clinically significant. Chiari 2 malformation may present a variety of clinical manifestations, which can include spinal symptoms secondary to myelomeningocele, tethered cord syndrome or syringomyelia, symptoms of secondary hydrocephalus, brainstem symptoms, or those due to lower cranial nerve dysfunction. The nosographic collocation of type 0 or 0.5 Chiari malformation or Chiari-like symptoms without tonsillar herniation, type 1.5 Chiari malformation between types 1 and 2, and complex Chiari is controversial and not universally accepted.